1. Field of the Invention
This invention relates to an air distribution system and, in particular, to an air distribution system for a vehicle cab.
2. Description of the Prior Art
Vehicles, such as agricultural tractors, typically employ means for protecting the vehicle operator from dust, noise and air temperature extremes. Ventilation systems to which this invention will apply, take fresh air in from the outside and deliver it, treated or untreated, to the interior of the cab.
In collecting air from the outside, large quantities of dust are also taken and must be removed before the air is transferred into the cab. The quantity of air will vary depending on the type of ventilation system in use. In some ventilation systems such as the constant pressurization system disclosed in U.S. Pat. No. 4,344,356 to Casterton, fresh air is used to pressurize the interior of the cab and keep dust from entering through other cracks and crevices within the cab body. Other ventilation systems take in large quantities of fresh air which are passed into the cab and vented out with no additional pressurization of the cab. In either case, the dust from the fresh air is typically collected by a filter.
Ordinary fresh air filters for vehicle cabs collect dust or airborne particulate material on the upstream surface of a filter face disposed between the air inlet and the vehicle cab outlet. These filters come in many shapes and configurations. In the past, fresh air filters were located in a chamber from which the filter could be extracted and cleaned. However, vibration of the vehicle would cause dust to fall off the face of the filter and collect in the chamber. The collection of dust in the chamber and the tendency of particles to fall off the filter made cleaning of the filter element an inconvenient and messy job. Such problems were exacerbated where the filter system was located in the roof of a vehicle cab along with the rest of the ventilation system. In such systems, dust and dirt would often fall on the operator when opening the chamber to take out the filter and perform cleaning.
In order to overcome some of the previously mentioned difficulties and also to reduce the required frequency of cleaning, filter elements have been located on the exterior of vehicle cabs. A filter of this type mounted on the rearward roof portion of a vehicle cab is shown in U.S. Pat. No. 3,868,896 issued to Dahl et al. The collection face of the filter in Dahl faces downward and is uncovered allowing particles to drop off along the back window of the vehicle cab. Another system along the lines of Dahl is disclosed in U.S. Pat. No. 4,072,487 issued to Irwin which shows a cylindrical filter in an open bottomed chamber. Air flow in the Irwin patent is radially inward so that dust collects on the exterior of the cylindrical filter element. Although the Dahl and Irwin patents overcome the problems of accumulated dirt in a filter chamber, these filters are still awkward and messy to clean. Furthermore, drop off from these filters causes additional dust and dirt particles to accumulate on the back window and rearward section of the tractor cab.
Accordingly, it is an objective of this invention to provide a ventilation system having a filter that traps dust and other airborne particulate material and prevents drop off of these particles.
It is a further objective of this invention to provide a filter that is easily and cleanly removed from an air filter chamber.
Other objects and advantages of the present invention will become more apparent to those skilled in the art in view of the following description and the accompanying drawings.